The invention relates to an electrical starter system for the retrofit of motorcycles, which starter system is to replace or complement the mechanical starter system, the so-called kick starter. For the sake of simplicity, the electrical starter system will hereinafter be called “the starter” and the mechanical starter system will be called “the kick starter”. The invention further relates to a motorcycle equipped with this starter system.
The crankshaft must be accelerated to a minimum speed to enable the engine of a motorcycle to start. This requires the generation of an external torque, which can be transmitted to the crankshaft directly or indirectly using a gearwheel, a belt, or a chain.
A kick starter is a lever consisting of a pedal and a kick arm. This lever is mostly fastened on the left side of the motorcycle. A rider's forceful kick of the kick starter generates a rotary motion which accelerates the crankshaft to the speed required for starting the engine. Kick starters were necessary before the invention of the starter, and they were very common before starters were installed as standard equipment. Many motorcycles of older model years are still equipped with a kick starter today.
The starter has gradually replaced the kick starter due to its increased convenience. The starter provides the rotary motion for motorcycles by means of an electric motor that is operated by a start button on the handlebar or on the electric motor itself. The shaft of the electric motor has a gearwheel, hereinafter called the starter shaft pinion, mounted to its end and transmits the resulting rotary motion to a drive gear, hereinafter called the starter gear. The starter button is pressed until the motorcycle rider hears that the engine has started.
In addition to direct transmission to the crankshaft, the rotary motion can also be transmitted indirectly via the transmission main shaft. In motorcycles of the Harley-Davidson brand, the engine and the transmission are housed in separate casings. The kick starter and starter therefore act via a starter gear onto the transmission main shaft from which the motion is passed on to the crankshaft of the engine via a so-called primary drive using a chain or belt.
Motorcycles of the Harley-Davidson brand built before 1964 were all originally equipped with a kick starter. Many owners are interested in retrofitting them with a starter because of the more convenient starting process. The problem is that the space required for the additional components (electric motor, switch, associated mounting brackets, starter shaft pinion, starter gear) were not anticipated and planned for. While all motorcycles of the Harley-Davidson brand built between 1936 and 1957 were designed for two different engine types, the panhead engine and the knucklehead engine, a specific variant of the unsprung rigid frame provided an overarching common feature. The shape of the rigid frame and the original components used then provide the basis for the concept, design and assembly of an electrical starter system for the retrofit of motorcycles of the Harley-Davidson brand built between 1936 and 1957.
A construction kit for the retrofit of motorcycles of the Harley-Davidson brand built in the respective period is known, for example, from TechCycle. The electric motor and the associated magnetic switch are screwed onto the transmission base plate on the rigid frame using two brackets. To provide the required space, the oil tank located above the electric motor must be replaced by a new design. To allow transmission of the rotary motion at the clutch to the transmission main shaft, the original primary drive (in its original design as a chain drive) must be replaced by a primary drive system of a later year of construction (this later design being a belt drive instead of a chain drive) in which a starter gear visible from outside is already integrated.
The disadvantage of this known construction kit is that the replacement of the primary drive system and the oil tank causes extra costs.
It is the problem of this invention to provide an improved electric starter construction kit for the retrofit of Harley-Davidson motorcycles built from 1936 to 1957 with a starter with as few visible constructional changes as possible. Owners of these old Harley-Davidson motorcycles are often interested in keeping the original components and in leaving the optical appearance of the motorcycle unchanged. Any components required in addition have to be designed and arranged such that the primary drive system, the oil tank, and the rear fender can still be used. Necessary processing steps of the original components or equivalent model year specific replacement parts should be performed such that they will not change the optical appearance of the motorcycle and retain the full functionality of the components.
The electrical starter system specified in claim 1 is proposed to solve this problem. The dependent claims disclose optional, advantageous embodiments of the invention.